A long term objective of this proposal is to determine to what degree putative affinities between regenerating retinal axons and the specific pathways that they traverse are responsible for the specificity that exists in the connections between the retina and tectum. A second objective is to determine the mechanism that mediates the complex axonal rearrangements that occur at the optic chiasm. Another objective is to understand the basis for an intraretinal boundary that separates dorsal and ventral retinal ganglion cells and how this boundary separates dorsal and ventral retinal ganglion cells axons within the optic nerve. A final goal is to understand how the retina is repaired following its partial destruction. The source of the cells that mediate the regenerative process will be determined. Furthermore, the ability of the regenerating retina to form a retinal specialization, such as a new area centralis, will also be examined. The information obtained in these studies will allow us to understand how specific connections are established during the course of optic nerve regeneration and the mechanisms that mediate retinal regeneration. Such information will help establish methods that are necessary to achieve central nervous system regeneration in species that lack this ability. The methods to be used include light microscopy of optic axons and retinal ganglion cells filled with cobaltous-lysine. Tritiated thymidine autoradiography will be used to study the histogenesis of retinal ganglion cells in relation to the establishment of the boundary between dorsal and ventral retina.